"""Page number start / offset helpers."""

from pathlib import Path
from zipfile import ZipFile

from docx import Document
from docx.oxml.ns import qn
from lxml import etree

from md2gost.page_geometry import (
    apply_page_number_start,
    apply_section_geometry,
    clear_section_page_start,
    patch_docx_page_starts,
    set_section_page_start,
)

_W = "{http://schemas.openxmlformats.org/wordprocessingml/2006/main}"


def _pg_start(section):
    pg = section._sectPr.find(qn("w:pgNumType"))
    if pg is None:
        return None
    return pg.get(qn("w:start"))


def test_set_section_page_start():
    doc = Document()
    section = doc.sections[0]
    set_section_page_start(section, 3)
    pg = section._sectPr.find(qn("w:pgNumType"))
    assert pg is not None
    assert pg.get(qn("w:start")) == "3"


def test_apply_page_number_start_skips_front():
    doc = Document()
    doc.add_section()  # front
    doc.add_section()  # body
    apply_page_number_start(doc, 2, front_sections=1)
    front = doc.sections[0]._sectPr.find(qn("w:pgNumType"))
    body = doc.sections[1]._sectPr.find(qn("w:pgNumType"))
    assert front is None or front.get(qn("w:start")) is None
    assert body is not None
    assert body.get(qn("w:start")) == "2"


def test_apply_page_number_start_none_strips():
    doc = Document()
    set_section_page_start(doc.sections[0], 5)
    apply_page_number_start(doc, None)
    pg = doc.sections[0]._sectPr.find(qn("w:pgNumType"))
    assert pg is None or pg.get(qn("w:start")) is None


def test_apply_page_number_start_none_strips_all_four_sections():
    doc = Document()
    for _ in range(3):
        doc.add_section()
    for section in doc.sections:
        set_section_page_start(section, 1)
    assert all(_pg_start(s) == "1" for s in doc.sections)

    apply_page_number_start(doc, None)
    assert all(_pg_start(s) is None for s in doc.sections)


def test_apply_page_number_start_body_only_with_front():
    doc = Document()
    for _ in range(3):
        doc.add_section()  # front + body + landscape + portrait = 4
    for section in doc.sections:
        set_section_page_start(section, 1)

    apply_page_number_start(doc, 1, front_sections=1)
    assert _pg_start(doc.sections[0]) is None
    assert _pg_start(doc.sections[1]) == "1"
    assert _pg_start(doc.sections[2]) is None
    assert _pg_start(doc.sections[3]) is None


def test_apply_section_geometry_strips_copied_start():
    doc = Document()
    set_section_page_start(doc.sections[0], 1)
    apply_section_geometry(doc.sections[0], landscape=True)
    assert _pg_start(doc.sections[0]) is None


def test_clear_section_page_start_removes_empty_element():
    doc = Document()
    set_section_page_start(doc.sections[0], 1)
    clear_section_page_start(doc.sections[0])
    assert doc.sections[0]._sectPr.find(qn("w:pgNumType")) is None


def test_patch_docx_page_starts_strips_and_restores(tmp_path: Path):
    doc = Document()
    for _ in range(3):
        doc.add_section()
    for section in doc.sections:
        set_section_page_start(section, 1)
    path = tmp_path / "pages.docx"
    doc.save(path)

    patch_docx_page_starts(path, None)
    with ZipFile(path) as z:
        root = etree.fromstring(z.read("word/document.xml"))
    starts = [
        el.get(f"{_W}start")
        for el in root.findall(f".//{_W}pgNumType")
    ]
    assert all(s is None for s in starts)

    # Re-seed starts then restore body-only restart.
    doc2 = Document(str(path))
    for section in doc2.sections:
        set_section_page_start(section, 1)
    doc2.save(path)

    patch_docx_page_starts(path, 2, front_sections=1)
    with ZipFile(path) as z:
        root = etree.fromstring(z.read("word/document.xml"))
    body = root.find(f"{_W}body")
    sects = []
    for child in body:
        if child.tag == f"{_W}sectPr":
            sects.append(child)
            continue
        if child.tag != f"{_W}p":
            continue
        p_pr = child.find(f"{_W}pPr")
        if p_pr is None:
            continue
        sect = p_pr.find(f"{_W}sectPr")
        if sect is not None:
            sects.append(sect)
    assert len(sects) == 4
    vals = [
        (s.find(f"{_W}pgNumType").get(f"{_W}start")
         if s.find(f"{_W}pgNumType") is not None else None)
        for s in sects
    ]
    assert vals[0] is None
    assert vals[1] == "2"
    assert vals[2] is None
    assert vals[3] is None